This invention relates in general to drive train systems for transferring rotational power from a source of rotational power to a rotatably driven mechanism. In particular, this invention relates to an improved driveshaft assembly for use in such a drive train system that is axially collapsible in the event of a collision to absorb energy and a method for manufacturing same.
Torque transmitting shafts are widely used for transferring rotational power from a source of rotational power to a rotatably driven mechanism. For example, in most land vehicles in use today, a drive train system is provided for transmitting rotational power from an output shaft of an engine/transmission assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical vehicular drive train system includes a hollow cylindrical driveshaft tube. A first universal joint is connected between the output shaft of the engine/transmission assembly and a first end of the driveshaft tube, while a second universal joint is connected between a second end of the driveshaft tube and the input shaft of the axle assembly. The universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of misalignment between the rotational axes of these three shafts.
A recent trend in the development of passenger, sport utility, pickup truck, and other vehicles has been to design the various components of the vehicle in such a manner as to absorb energy during a collision, thereby providing additional safety to the occupants of the vehicle. As a part of this trend, it is known to design the drive train system of vehicles so as to be axially collapsible so as to absorb energy during a collision. To accomplish this, the driveshaft tube may be formed as an assembly of first and second driveshaft sections that are connected together for concurrent rotational movement during normal operation, yet are capable of moving axially relative to one another when a relatively large axially compressive force is applied thereto, such as can occur during a collision. A variety of such axially collapsible driveshaft assemblies are known in the art.
It has been found to be desirable to design axially collapsible driveshaft assemblies of this general type such that a predetermined amount of force is required to initiate the relative axial movement between the two driveshaft sections. It has further been found to be desirable to design these axially collapsible driveshaft assemblies such that a predetermined amount of force (constant in some instances, varying in others) is required to maintain the relative axial movement between the two driveshaft sections. However, it has been found somewhat difficult to accurately control the amount of force that is required to initiate and subsequently maintain the axially collapsing of known driveshaft assemblies. Thus, it would be desirable to provide an improved driveshaft assembly for use in a drive train system that is axially collapsible in the event of a collision to absorb energy and a method for manufacturing same.
This invention relates to an improved driveshaft assembly for use in a drive train system that is axially collapsible in the event of a collision to absorb energy and a method for manufacturing same. The driveshaft assembly includes an inner tube that is received within an outer tube in an overlapping or telescoping manner. A plurality of external splines are formed on the inner tube, such as by deforming portions of the inner tube radially inwardly. Then, the outer tube is disposed about the inner tube, preferably in a press fit relationship. Next, portions of the outer tube are deformed radially inwardly about the inner tube. The radially inwardly deformed portions of the outer tube that extend between the external splines of the inner tube define internal splines on the outer tube. The internal splines formed on the outer tube cooperate with the external splines formed on the inner tube to provide a rotational driving connection between the inner tube and the outer tube, while normally preventing relative axial movement therebetween. However, if a relatively large axial force is applied to the ends of the driveshaft assembly, some or all of the splines will deform, allowing relative axial movement to occur between the inner tube and the outer tube. The splines may extend parallel to the rotational axis of the inner and outer tubes, or alternatively may be tapered relative to the inner tube.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.